FDA expands approval of Pfizer's HYMPAVZI for hemophilia treatment

Pfizer (NYSE:PFE) announced on June 8, 2026, that the U.S. Food and Drug Administration (FDA) has granted an expanded indication for HYMPAVZI® (marstacimab-hncq). The therapy is now approved for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and pediatric patients 6 years of age and older with hemophilia A or B, both with and without inhibitors.

This approval represents a significant development for the hemophilia community, particularly for patients who have developed inhibitors—antibodies that can render traditional factor replacement therapies ineffective. Previously, treatment options for these patients were often limited and burdensome. HYMPAVZI, a tissue factor pathway inhibitor (TFPI) antagonist, provides a non-factor treatment alternative that is administered via a once-weekly subcutaneous injection. Notably, the treatment does not require routine, labor-intensive laboratory monitoring, simplifying the management of the disease for both patients and caregivers.

The expanded approval is backed by robust clinical data. The efficacy and safety for patients 12 years and older with inhibitors were established by the Phase 3 BASIS trial, which demonstrated that HYMPAVZI significantly reduced the mean annualized bleeding rate (ABR) by 93% compared to on-demand treatment with bypassing agents. Furthermore, the approval for pediatric patients aged 6 to 11 years—including those with hemophilia B, who previously lacked a subcutaneous non-factor treatment option—was supported by interim results from the Phase 3 BASIS KIDS study.

“For children who have to deal with bleeding episodes from an early age and for people living with hemophilia who develop inhibitors, treatment options have been limited and are often burdensome,” said Dr. Guy Young, Director of the Hemostasis and Thrombosis Center at Children's Hospital, Los Angeles. He noted that the therapy's combination of bleed reduction and simple, once-weekly administration has the potential to fundamentally change how patients and caregivers approach disease management.

Pfizer continues to evaluate the long-term safety and efficacy of HYMPAVZI through ongoing open-label extension studies. This regulatory milestone reinforces the company's long-standing commitment to the hemophilia community, evolving from early recombinant factor therapies to modern, patient-centered subcutaneous treatments.

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